1. Field of the Invention
This invention relates to a device for connecting the feed for a fluid pressure system.
More particularly, the invention relates to a device for connecting the feed for a pressure fluid system, of the type in which a connector comprises a head adapted to be received axially in a body of a feed inlet, and of the type in which the connector is adapted to be locked in position before being engaged axially in the feed inlet body by locking means.
2. Description of the Related Art
It is known to make use of connectors of this type, also referred to as plug-in connectors, in order to make the connection in a feed pipe on the inlet of a hydraulic member in a simple and inexpensive way.
Such a coupling device for a feed of a fluid pressure system is for example known from the document FR-A-2 736 136.
That document describes more particularly a device of the type in which a connector is adapted to be held in its engaged position, axially within the feed inlet of a receiver member, by retaining means, and in which there are arranged, firstly a purge orifice of the receiver member and secondly a sealing ring disposed between the head of the connector and the feed inlet, the connector sealingly obturating the purge orifice in the engaged position, which is also called the locking position, and being able to occupy a position called the purge position, in which it is partly retracted axially towards the rear and in which it is held by retaining means, the feed inlet being put into communication sealingly with the purge orifice.
It is known from the said document to provide retaining means which consist of a clip or hairpin with two branches constituting a U, which is engaged transversely in the feed inlet body in such a way as to cooperate with a radial annular groove formed in the outer cylindrical surface of the connector.
More precisely, each branch of the clip comprises a cylindrical first portion and a cylindrical second portion of larger diameter, the cylindrical first portion co-operating with either a first or rear groove or a second or front groove, these grooves being formed in the connector for retaining it in the locking and purge positions respectively.
The second portion, having the larger diameter, enables passage from the locking position to the purge position to be achieved. More precisely, operation of the device will be explained below.
First, in order to put the device in its operating state, that is to say in its locked position, the operator has to proceed successively in the following way:                the connector is introduced into the body until it reaches its most advanced front axial position, and        the clip is then engaged transversely in the body until the first cylindrical portion of the clip positions itself in the annular first or rear groove of the connector.        
It is not easy for the operator to connect the device in its locking position, because it is necessary that the first or rear groove shall be in axial coincidence with the locking means.
Subsequently, when the operator wants to put the device in its purge position, he has successively to carry out the following:                first, to exert a first pulling force on the clip in order to cause it to be partly withdrawn out of the body in a straight-line movement, until the second cylindrical portion having the larger diameter is positioned in axial coincidence with the connector, so as to permit axial separation towards the rear, and        second, to withdraw the connector axially towards the rear.        
The locking means are then in an unlocked position. As will be understood, the axial rearward separation of the connector in order to pass from the locking position to the purge position is only possible if the cylindrical second portion having the larger diameter is correctly positioned, that is to say it is in perfect axial coincidence with the connector. Now since there is no way that the operator can control this good positioning by eye, it is necessary to proceed by trial and error, which is not satisfactory for various reasons.
Among these reasons may be mentioned the time which can be necessary for the operator to position the connector in its purge position, and this is incompatible with production requirements, particularly in the case where these assembly operations are carried out on production lines for motor vehicles in which each operation is scrupulously timed.
These problems do of course occur as much for an operator during the first time the operation is carried out as later on during maintenance operations on the vehicle.
However, the operations just described are only the first set of steps to be effected by the operator before the purge can actually be used. In this connection, when the operator has reached the correct position of the cylindrical second portion, and has therefore axially disengaged the connector towards the rear, he still cannot carry out the purge because he must first absolutely carry out a second set of operations.
This second set of operations consists in particular in the operator re-engaging the clip transversely so as to ensure retention of the connector, that is to say he must reposition the first cylindrical portion in the front groove corresponding to the purge position. Now here again, this operation is only possible if the connector, and therefore the front groove, is correctly positioned with respect to the clip.
Apart from the fact that the second set of operations on the device has the same disadvantages as before, it gives rise above all to an additional safety problem.
A purge operation is necessary to expel any gas such as air which has been able to enter the device, and more particularly into a hydraulic member such as a receiver, thereby guaranteeing proper subsequent operation of the device.
To this end, the operator carries out the purge of the system, that is to say he causes fluid to flow under pressure within the hydraulic member, for example by reducing the pressure. However, it is absolutely necessary that he has first re-engaged the clip in such a way that the cylindrical first portion is correctly positioned. In default of this, retention of the connector is not guaranteed, and under the action of the fluid pressure, there is a danger of the connector being expelled violently out of the feed inlet body.
The document DE-A-199.60.431 describes locking means between a first member and a second member which is attached on the first.
These means consist of a U-shaped hairpin member, generally cylindrical and also comprising a gripping portion formed in a connecting portion between the two branches of the hairpin. The branches include locking portions and stop fingers at the free end of each branch which cooperate with ramps forming part of the first member.
The hairpin is mounted in a slot in a supplementary intermediate member which is clipped axially on the first member.
In order to be able to proceed with assembly or disassembly, it is necessary to put the hairpin in an unlocking position whereby to be able to introduce or withdraw the two members axially.
To this end, it is necessary to exert on the gripping or connecting portion a transverse pulling force radially outwards, the effect of which, in conjunction with the mating cooperation of the stop fingers of each of the branches with the ramps of the first member, is to cause the branches to move apart in a radially outward direction, so that the locking portions are no longer in contact with the second member. This displacement of the stop fingers on the ramps is limited by safety notches against which the fingers come into abutment, and it is therefore impossible for the finger to be removed accidentally while the pulling release force is being exerted on the latter. Once this traction force ceases to be exerted, the hairpin regains its initial locking position due to the elasticity of its branches.
The features disclosed in the said document may be seen as lying principally in the use of the elastic deformation of the locking branches by mating cooperation with the ramps.
However, the initial fitting of the hairpin necessitates an additional intermediate member and can only be carried out in an axial, and not a radial, direction.
In addition, the force exerted on the connecting portion between the two branches of the hairpin, for the purpose of unlocking it, is a tractive force which is not natural for an operator, and which is in particular difficult to maintain during the unlocking operation.